REACTION MECHANISM OF METHANATION ON IRON CATALYST

概要

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Transient experiments were carried out at 250℃ under atmospheric pressure in order to elucidate qualitatively the reaction mechanism of methanation on a commercial fused iron catalyst. After the catalyst in the steady state was treated by helium for certain periods, a reaction mixture of 10% carbon monoxide in hydrogen was again introduced to the catalyst. These helium-treated catalysts showed no substantial induction period for methane formation, whereas the freshly reduced catalyst showed a 60-minute period of induction. With increasing period of the helium treatment, the rate of methane formation at the new steady state decreased. On the other hand, similar treatment by hydrogen flushing enhanced temporarily the rate of methane formation, which then regained the original steady state within 15 minutes. The rate of methane formation in the new steady state after the helium flushing decreased in proportion to increased amounts of water removed during the helium treatment. Increase in the methanation rate after the hydrogen treatment was closely related to the amount of surface oxygen species removed by hydrogen. The reaction intermediate on the working surface is discussed in accordance with the scheme reported in the previous papers of this series.
〔長崎大学教養部〕の論文